A Unique Pathway for the 3-Aminobutyrate Starter Unit from l-Glutamate through β-Glutamate during Biosynthesis of the 24-Membered Macrolactam Antibiotic, Incednine
摘要:
Incednine is a 24-membered macrolactam antibiotic produced by Streptomyces sp. ML694-90F3. A previous study demonstrated that its unique nitrogen-containing starter unit was derived from L-glutamate. To elucidate the missing link between L-glutamate and the starter unit, deuterium labeled amino acid feeding experiments were conducted. These experiments revealed that 3[3-H-2]aminobutyrate end beta-[2,2,4,4-H-2(4)]glutamate were incorporated into the starter moiety. The results indicate that a novel decarboxylation of beta-glutamate to give 3-aminobutyrate is involved in incednine biosynthesis.
Synthesis of [4-2H2]-, (4R)[4-2H1]- and (4S)[4-2H1]- 4-(methylnitrosamino)-1-(3'-pyridyl)-1-butanone, c-4 deuteriated isotopomers of the procarcinogen nnk
作者:Tanmaya Pathak、Noel F. Thomas、Mahmoud Akhtar、David Gani
DOI:10.1016/s0040-4020(01)81978-5
日期:1990.1
The synthesis of C-4 dideuteriated and both C-4 monodeuteriated enantiomers of NNK, the metabolic precursor to a variety of potential carcinogens, starting from (2S)-glutamic acid and nicotinic acid is described. The route is suitable for the synthesis of NNK isotopomers labelled in each of the putative sites for metabolic activation.
<i>Cis</i>/<i>trans</i>stereochemical effects in the negative chemical ionization/OH<sup>−</sup>mass spectra of strained-ring azabicycloalkanes using MIKE and CA/MIKE spectrometry
AbstractStereospecific decomposition reactions of isomeric (cis and trans) deprotonated molecules from azabicycloalkane derivatives as azetidinols generated under negative chemical ionization (NCI)/OH− have been examined using mass‐analysed ion kinetic energy (MIKE) and collisional activation (CA)/MIKE spectra. These measurements together with the ones obtained on specifically labelled compounds enabled us to determine the origin of the stereochemical effects. The results indicate that the hydroxylic proton constitutes the preferential (≃90%) site for the deprotonation process. Subsequent fragmentations of the deprotonated species observed in the second field‐free region of a reversed geometry instrument are affected by the stereochemistry of the hydroxylic group. The isomer with the hydroxyl group in the cis position relative to the hydrogen at the ring junction mainly loses H2O, while the trans isomer eliminates CH3˙, both processes occurring with high specificity. Labelling studies indicate that two major pathways exist for the elimination of H2O from the cis isomer and the loss of CH3˙ from the trans isomer. The course of the reaction is determined by the ability of the stereoisomers to transfer a proton during the first decomposition step. When the size of the lactam ring is increased from a five‐membered ring to a six‐ or seven‐membered ring, these stereochemical effects tend to become less pronounced.
PATHAK, TAMMAYA;THOMAS, NOEL F.;AKHTAR, MAHMOUD;GANI, DAVID, TETRAHEDRON, 46,(1990) N, C. 1733-1744
作者:PATHAK, TAMMAYA、THOMAS, NOEL F.、AKHTAR, MAHMOUD、GANI, DAVID